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[Offline Pages] Add network status, save request textbox, and offline url link to offline internals page

BUG=629880,629879
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2172443004
Cr-Commit-Position: refs/heads/master@{#407332}